This invention is related to security tags, and, in particular, to providing RFID tags and attaching such tags onto pallets and cartons in high volume.
The two largest components of the cost of RFID tags today are the integrated circuit (IC) and the attachment of that IC to an antenna structure. Moore's Law and increasing volume of RFID tags being made are helping to drive the IC cost down, but the primary method for attachment of the IC to the antenna structure is bonding. Bonding is a mechanical process that does not benefit from the same technology advances or economies of scale as the manufacture of an IC.
Current methods of chip bonding do not adequately address cost. A two-step approach of an intermediary “strap” achieves incremental cost improvement by relocating the costs. However, straps do not address the problem directly, as bonding is still required, but to a smaller tag. Moreover, straps add another step to bond the strap to the big tag.
Current manufacturers using standard bonding technology with straps want straps to be like traditional bonding surfaces, that is, hard and inflexible. But such straps do not lend themselves to easy integration into soft flexible tags. The known standard bonding processes are all strap-based solutions, and therefore less than ideal.
Standard electronic chip components are known and generally found on printed circuit boards. A bare IC is bonded to a carrier by wire bonding or flip chip bonding (a technique where the IC is bonded face down to the carrier). Then a package is molded around the carrier and chip. The package is then put onto a printed circuit board via thru-hole or surface mount assembly. Standard chip components need to be compatible with multiple printed circuit board assembly technologies (including solder baths, solder waves, IR reflow, and a variety of cleaning and baking steps), want more and more computational power put in single chip assemblies, and must be made to last.
In contradistinction, RFID tags are never soldered or baked or cleaned. RFID tags are complete unto themselves and do not have to be integrated into any other system. They require a bare minimum of computational power to minimize cost and energy consumption (which translates into read distance), and do not face the same power dissipation or environmental requirements as standard chips.
RFID tags are substantially different that standard electronic chip components. The metal layer is thin and flexible (or non-rigid) by comparison. The back or substrate of each tag is soft polypropylene or paper. The substrates are easy to punch, cut, dimple, and weld.
In designing an efficient chip placement process that can be integrated into RFID tags, it is beneficial to avoid anything that is not consistent with a continuous rolling printing press. Stopping and starting the line always slows things down. It would be beneficial to adjust tooling to operate on a chip that is continuously advancing down the line at a known rate of travel.
Retracing a path during the bonding process takes time, causes vibration, and wears mechanical linkages. These linkages also create uncertainty in absolute position. Rotating or continuous devices are thus preferred over reciprocating devices.
The greater the number of mechanical connections in a bonding process, the less certainty there is in precise position. Every jointed or flexible linkage introduces a certain amount of randomness as the web and chips wiggle around. IC dimensions are tiny. Movement of chips out of critical alignment is easily possible.
When manufacturing security tags, one cannot rely on any precise dimension set previously in a prior step. The relative position of things varies across the web, from one end of the roll to another, from place to place, and from time to time. That is simply the reality of working with inexpensive materials. For IC bonding processes, the manufacturer must constantly adapt to how the material is really behaving, rather than counting on it to behave as intended.
It would be beneficial to have a placement system for an IC on an antenna to create an RFID tag that operates at higher speeds than current systems for placement on cartons and pallets, is inexpensive and reliable to operate, and that provides high quality and reliable tags.
All references cited herein are incorporated herein by reference in their entireties.